Chainsaw Repair

also remember the gauge itself makes a difference , I know on my gauge 200 psi will sound good but unless you are running real good fuel it will fall flat on its face in big wood . On say a 281 woodsport saw I can make 200 psi like nothing but in about the 3rd or 4 cut in 20 inch plus wood I can feel it start to slow down so I keep those saws at 175 psi and no trouble , BEMP is what you  have to look at but also remember the smaller the bore the higher you can run your BEMP but also just because the computer says it will work with a 19.9 to 1 compression  it lies to sometimes  , on gas if you are getting real close to the edge once you make a run in say 3 cuts in 8 by 8 , shut the motor off and open up the throttle and listen, you should be able to hear the gas boil in the crankcase and in most cases if you can hear this , you have went to far with either compression, ignition timing to advanced or if running a pipe the pipe is drawing to hard on the transfer ports

See Al this is where I have a big problem with compression ratios on 2 strokes , everyone talks about 14 to 1 or 16 to 1  but they are counting the whole cc's of the engine from BDC to TBC, to me this is pure BS cause you got ports in that area so that volume is totally wrong , reason , if you have 2 motors the same type but 1 motor has the ext. port timing at 100 degrees ATDC and the other has its 80 degrees ATDC , both engines would have the same compression ratio by using this method but the amount of compression each will make it totally different , To me the proper way is to only count the number of cc's above the ext. port to get your compression ratio

But, you can make lots of psi by  stuffing a small space..... but have no flow.  What would you rather have, a 7cc chamber at 240psi, or a 11cc chamber at 170psi?  I don't know the anwser,  there will be more air/fuel trapped in the bigger head, but more pressure in the small one..... 

Al that is why I go with PSI instead  of Compression ratio , yes you still have to think cause you can still build a motor where it fights itself all the way instead of working like you think it should  plus when you throw a pipe into this mess it changes everything again and what fuel you are using makes all the difference in the world

It usually starts with little pin holes burned in the piston top.

Sometimes the pin holes are around the plug area and other times they are around the squish more towards the exhaust.

You can often hear the noise. The saw will not sound right.